There is an increasing demand for alkylate fuel blending feedstock. As a fuel-blending component alkylate combines a low vapour pressure, no sulphur, olefins or aromatics with high octane properties.
Almost all alkylate is produced by reacting isobutane with butene in the presence of a suitable acidic catalyst. The most used catalysts are HF and sulphuric acid, although other catalysts such a solid acid catalyst have been reported. Recently, the alkylation of isoparaffins with olefins using an acidic ionic liquid catalysts has attracted attention as an alternative to HF and sulphuric acid catalysed alkylation processes.
In for instance U.S. Pat. No. 7,285,698 a process for manufacturing an alkylate oil is disclosed, which uses a composite ionic liquid catalyst to react isobutane with a butene. In the process of U.S. Pat. No. 7,285,698, isobutane and butene are supplied to a reactor and the alkylate is formed by contacting the reactants with an composite ionic liquid under alkylation conditions. The reactor effluent is separated and the ionic liquid phase is recycled to the reactor while the hydrocarbon phase is treated to retrieve the alkylate. Although, the process of U.S. Pat. No. 7,285,698 shows that the use of an ionic liquid catalyst allows for the preparation of a good alkylate fuel blending component, there is still a need in the art for an improved ionic liquid alkylation process.